Method and Apparatus for Handling Random Access Procedure in a Wireless Communications System

ABSTRACT

A method for handling a random access procedure in a user equipment, called UE hereinafter, of a wireless communications system, the UE assigned a dedicated preamble for the random access procedure, the method includes deciding whether to reuse the dedicated preamble when the UE doesn&#39;t receive a downlink message successfully or the random access procedure is failed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/895,987, filed on Mar. 21, 2007 and entitled “Method and Apparatus toimprove LTE Random access procedure”, and the benefit of U.S.Provisional Application No. 60/945,948, filed on Jun. 25, 2007 andentitled “Method and Apparatus to optimize Random Access Procedure”, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for handlingrandom access procedure in a wireless communications system, and moreparticularly, to a method and apparatus for implementing timingalignment and resource request, so as to enhance system efficiency.

2. Description of the Prior Art

The third generation mobile telecommunications system (called 3G system)provides high frequency spectrum utilization, universal coverage, andhigh quality, high-speed multimedia data transmission, and also meetsall kinds of QoS requirements simultaneously, providing diverse,flexible, two-way transmission services and better communication qualityto reduce transmission interruption rates. However, due to demand forhigh-speed and multimedia applications, the next generation mobiletelecommunications technology and related communication protocols havebeen developed.

In the Long Term Evolution wireless communications system (LTE system),a Random Access Channel (RACH) is configured in an uplink (UL) channelbetween a user equipment (UE) and the network, and utilized for timingalignment, RNTI (Radio Network Temporary Identifier) assignment, andresource request. In the starting state, only downlink (DL) timingbetween UE and Node B (NB) is synchronized, and signals on RACH can beused for UL timing alignment. Before performing UL timing alignment, UEuses downlink Synchronization Channel or reference signals to performsynchronization on timing and frame. However, since signals may bedelayed due to a distance between the transmitter and receiver, UE isnot able to determine whether a message transmitted from UE is at astarting position of a receiving frame of NB. In addition, when NBprovides service for multiple UEs at the same time, Round Trip Delays(RTDs) between each UE and NB may be different due to differentdistances thereof, causing timing offset. Therefore, NB evaluates timingoffset of a UE according to RACH signals from the UE, and notifies theUE to adjusting UL timing via Downlink Shared Channel (DL-SCH), toachieve timing synchronization. A RACH signal is composed of preamblesused for UL timing synchronization and UE identity detection, orcarrying short signaling or signature.

On the other hand, RACH signals among different UEs are transmitted toNB by contention-based or non-contention-based method. That is, UE canselect a RACH transmission opportunity and randomly select a preamble totransmit signals, or transmit a signal carrying a preamble assigned bythe network (in such a situation, the RACH transmission opportunity isassigned by the network or selected by the UE). If the network cannotidentify the transmitted RACH signal due to collision or low power, orif contention lost occurs due to a randomly-selected preamble, the UEcan retransmit the RACH signal with larger power in the next availableRACH transmission opportunity, until a response from the network isreceived or a condition is reached, e.g., maximum transmitting ormaximum power.

For LTE, a RACH transmission opportunity is related to a time-frequencyradio resource, not only related to time or frequency. Therefore, whenRACH physical resource is selected, its time period and frequency bandare determined. Of course, at certain time period, there may be morethan one frequency sub-band for selection. On the other hand, preamblecan be random access preamble, which is randomly selected by UE, ordedicated preamble, which is assigned by network (source cell or targetcell). Basically, when UE uses (randomly selected) random accesspreamble, there is possibility another UE use the same preamble andtransmit it in the same RACH opportunity so that network doesn't knowwhether the signal comes from one or more than one UE. Consequently,contention exists and will be solved after UE sends its UE identity insubsequent message 3. In contrary, dedicated preamble is assigned bynetwork to a known specific UE so it's unique and won't cause contentionbetween UEs (no another UE use the same dedicated preamble.)

In LTE, asynchronous RACH is concluded and adopted as working assumptionwhere dedicated preamble and random access preamble based RACH accessesmay both be supported. Random access procedure performance mainly interms of latency and overhead is affected by collision/contentionprobability, time/frequency resources, number of user equipments (load),number of preamble signature, channel quality, UE identities, and evenaccess causes and so on. On the other hand, the design requirements inaddition to performance, such as short life span of identity usage, tobe common for various kinds of non-synchronous RACH accesses in E-UTRAN(eNB and aGW) for FDD and TDD as well as irrespective of cell size,optimization for connected state UEs, are considered while possiblereasons for UE to access on RACH can be categorized into four maincauses, which are initial access (e.g. UE originated call, networkoriginated call, tracking area update and initial cell access) includinginitial NAS signaling for NAS procedures (e.g. service request, networkattach, routing/tracking area update), synchronization request, handoveraccess and scheduling request. According to requirements and need ofsupport for possible access causes, the baseline random access proceduremodel and channel mapping (between logical channels and transportchannels) are defined in the prior art. Current decision on four stepsof random access procedures is shown as following:

(1) Step “Random Access Preamble on RACH in uplink”: is corresponding toa message 1, which carries 6 bits, and indicates a random ID, andpossibly other information, e.g., cause or size, potentially withpriority, pathloss or CQI to allocate UL resource appropriately.

(2) Step “Random Access Response on DL-SCH”: is corresponding to amessage 2, which is semi-synchronous (within a flexible window of whichthe size is one or more TTI) with message 1, no HARQ (Hybrid AutomaticRepeat Request) support, transmitted on L1/L2+DL-SCH, addressed toRA-RNTI (Random Access RNTI) on L1/L2 control channel, conveys at leastRA-preamble identifier, timing alignment information, initial UL grantand assignment of Temporary Cell RNTI (T-CRNTI), and is intended for oneor multiple UEs in one DL-SCH message.

(3) Step “First scheduled UL transmission on UL-SCH”: is correspondingto a message 3, which uses HARQ, operates in RLC TM (Radio Link ControlTransparent Mode) without segmentation, conveys at least UE identifierand (explicit or implicit) information on whether C-RNTI is alreadyavailable. Besides, in case of initial access and if the size of themessage allows it, the initial NAS message (or something allowing tobuild the initial NAS message in eNB) can be included, and size of themessage is dynamic.

(4) Step “Contention Resolution on DL-SCH”: is corresponding to amessage 4, which is not synchronized with message 3, and addressed tothe Temporary C-RNTI on L1/L2 control channel (at least for initialaccess). Besides, content of the message is FFS (for further study),HARQ is supported, and HARQ feedback is transmitted only by the UE whichdetects its own UE identity, as provided in message 3, echoed in the RRC(Radio Resource Control) Contention Resolution message.

In the prior art, at initial access, the four steps are: Random AccessPreamble on RACH, Random Access Response via CCCH (Common ControlChannel) on DL-SCH, RRC Connection Request via CCCH on UL-SCH, and RRCContention Resolution via DCCH on DL-SCH.

Therefore, for LTE, the prior art provides steps of RA procedure.However, some problems may occur.

HARQ is not supported for message 2. Therefore, during random accessprocedure or RACH access if a UE with assignment of dedicated preambledoesn't successfully receive message 2 which might have been sent out bynetwork, the dedicated preamble is wasted. It's not specified when/underwhat conditions the dedicated preamble for a UE should be withdrawn bynetwork and how dedicated preamble shall be used efficiently even thoughit's critical. If the UE with dedicated preamble failed at random accessresponse reception, it may reuse dedicated preamble for contention-lessrandom access again or consider to use random access preamble if the UEassume the dedicated preamble is released (e.g. after several times ofrandom access attempt). A standardized rule should be specified to avoidmisunderstanding on usage and assignment of dedicated preamble betweenUE and network. Otherwise, a dedicated preamble may not be released oreven increase the contention probability.

Network can pre-assign dedicated preamble to UE for synchronizationrequest (e.g. when UE loses synchronization or when there is a UEoriginated call) or scheduling request. However, the dedicated preambleshould be reserved and dynamically assigned to UE when only it'snecessary. It's of course insufficient to provide non-contention basedRA to a large number of connected state users (including UEs inlong_DRX). On the other hand, to make the dedicated preamble assignmentefficient, if a UE requires two different random access procedures orRACH access consecutively for different reasons (e.g. synchronizationrequest and scheduling request), it's not efficient to waste time/radioresources at issuing a dedicate preamble (e.g. new or old one),especially while the dedicated preamble may be reused again /releasedlater if two UEs are initiating random access procedure or RACH accessof equal priority.

In LTE RACH access, the coexistence of dedicated preamble and randomaccess preamble should be considered for certain circumstance,especially when available preambles are sufficient or concurrentprocedures (e.g. time critical and non-time critical) are performed by aUE.

SUMMARY OF THE INVENTION

According to the claimed invention, a method for handling a randomaccess procedure in a user equipment, called UE hereinafter, of awireless communications system, the UE assigned a dedicated preamble forthe random access procedure, the method comprises deciding whether toreuse the dedicated preamble when the UE doesn't receive a downlinkmessage successfully or the random access procedure is failed.

According to the claimed invention, a method for handling a randomaccess procedure in a network of a wireless communications systemcomprises receiving a dedicated preamble for an access of a randomaccess channel from a user equipment, called UE hereinafter; respondingto the UE via a message 2; and when a message 3 is not successfullyreceived within a specified duration or a scheduling resource,determining whether the UE reuses the dedicated preamble for next randomaccess attempt.

According to the claimed invention, a method for handling a randomaccess procedure in a user equipment, called UE hereinafter, of awireless communications system, the UE assigned a dedicated preamble forthe random access procedure, the method comprises outputting a dedicatedpreamble for an access of a random access channel to a network;receiving a response from the network in a message 2; and determiningwhether to reuse the dedicated preamble according to a response from thenetwork or whether the response is received.

According to the claimed invention, a method for handling a randomaccess procedure in a network of a wireless communications systemcomprises receiving a message 3 from a user equipment, called UEhereinafter; outputting an acknowledgement to respond the receivingstatus of the message 3; and determining whether a dedicated preamble ofthe UE can be reused or released according to a standardized rule orconfiguration.

According to the claimed invention, a method for handling a randomaccess procedure in a user equipment, called UE hereinafter, of awireless communications system comprises using a dedicated preamble fora first random access procedure; and reusing the dedicated preamble fora second random access procedure later than the first random accessprocedure according to a standardized rule or configuration.

According to the claimed invention, a method for handling a randomaccess procedure in a network of a wireless communications systemcomprises assigning a dedicated preamble for a user equipment, called UEhereinafter, for the random access procedure; and determining whetherthe dedicated preamble can be reused for another access of a randomaccess channel or another random access procedure according to astandardized rule or configuration.

According to the claimed invention, a method for handling a randomaccess procedure in a user equipment, called UE hereinafter, of awireless communications system, the UE assigned a dedicated preamble forthe random access procedure, the method comprises using the dedicatedpreamble in an access of a random access channel according toconfiguration indicated by a control message from an upper layer.

According to the claimed invention, a method for handling a randomaccess procedure in a network of a wireless communications systemcomprises assigning a dedicated preamble for a user equipment, called UEhereinafter, for an access of a random access channel via a downlinkmessage or signaling or an indication or information field when therandom access procedure is triggered, confirmed, or expected by thenetwork.

According to the claimed invention, a method for handling a randomaccess procedure in a network of a wireless communications systemcomprises allowing the coexistence of a dedicated preamble and a randomaccess preamble corresponding to a user equipment, called UEhereinafter, according to a standardized rule or configuration.

According to the claimed invention, a method for handling a randomaccess procedure in a user equipment, called UE hereinafter, of awireless communications system comprises allowing the coexistence of adedicated preamble and a random access preamble for a UE for at leasttwo random access procedures.

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises the communications device assigned a dedicated preamble forthe random access procedure; and deciding whether to reuse the dedicatedpreamble when the UE doesn't receive a downlink message successfully orthe random access procedure is failed.

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises receiving a dedicated preamble for an access of a randomaccess channel from a user equipment, called UE hereinafter; respondingto the UE via a message 2; and when a message 3 is not successfullyreceived within a specified duration or a scheduling resource,determining whether the UE reuses the dedicated preamble for next randomaccess attempt.

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises the communications device assigned a dedicated preamble forthe random access procedure; outputting a dedicated preamble for anaccess of a random access channel to a network; receiving a responsefrom the network in a message 2; and determining whether to reuse thededicated preamble according to a response from the network or whetherthe response is received

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises receiving a message 3 from a user equipment, called UEhereinafter; outputting an acknowledgement to respond the receivingstatus of the message 3; and determining whether a dedicated preamble ofthe UE can be reused or released according to a standardized rule orconfiguration.

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises using a dedicated preamble for a first random accessprocedure; and reusing the dedicated preamble for a second random accessprocedure later than the first random access procedure according to astandardized rule or configuration.

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises assigning a dedicated preamble for a user equipment, called UEhereinafter, for the random access procedure; and determining whetherthe dedicated preamble can be reused for another access of a randomaccess channel or another random access procedure according to astandardized rule or configuration.

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises the communications device assigned a dedicated preamble forthe random access procedure; and using the dedicated preamble in anaccess of a random access channel according to configuration indicatedby a control message from an upper layer.

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises assigning a dedicated preamble for a user equipment, called UEhereinafter, for an access of a random access channel via a downlinkmessage or signaling or an indication or information field when therandom access procedure is triggered, confirmed, or expected by thenetwork.

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises allowing the coexistence of a dedicated preamble and a randomaccess preamble corresponding to a user equipment, called UEhereinafter, according to a standardized rule or configuration.

According to the claimed invention, a communications device foraccurately handling a random access procedure in a wirelesscommunications system comprises a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises allowing the coexistence of a dedicated preamble and a randomaccess preamble for a UE for at least two random access procedures.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a function block diagram of a wireless communications device.

FIG. 2 is a diagram of program code of FIG. 1.

FIG. 3 to FIG. 11 are flowcharts of processes according to embodimentsof the present invention.

FIG. 12 is a schematic diagram of a wireless communications system.

DETAILED DESCRIPTION

Please refer to FIG. 12, which illustrates a schematic diagram of awireless communications system 1200. The wireless communications system1200 is preferably an LTE system, and is briefly composed of a networkand a plurality of UEs. In FIG. 12, the network and the UEs are simplyutilized for illustrating the structure of the wireless communicationssystem 1200. Practically, the network terminal may comprise a pluralityof base stations (or Node B), radio network controllers and so onaccording to actual demands, and the UEs can be devices such as mobilephones, computer systems, etc.

Please refer to FIG. 1, which is a functional block diagram of acommunications device 100. The communications device 100 can be used forimplementing the network and the UE shown in FIG. 12. For the sake ofbrevity, FIG. 1 only shows an input device 102, an output device 104, acontrol circuit 106, a central processing unit (CPU) 108, a memory 110,a program code 112, and a transceiver 114 of the communications device100. In the communications device 100, the control circuit 106 executesthe program code 112 in the memory 110 through the CPU 108, therebycontrolling an operation of the communications device 100. Thecommunications device 100 can receive signals input by a user throughthe input device 102, such as a keyboard, and can output images andsounds through the output device 104, such as a monitor or speakers. Thetransceiver 114 is used to receive and transmit wireless signals,delivering received signals to the control circuit 106, and outputtingsignals generated by the control circuit 106 wirelessly. From aperspective of a communications protocol framework, the transceiver 114can be seen as a portion of Layer 1, and the control circuit 106 can beutilized to realize functions of Layer 2 and Layer 3. Preferably, thecommunications device 100 is utilized in a third generation (3G) mobilecommunications system.

Please continue to refer to FIG. 2. FIG. 2 is a diagram of the programcode 112 shown in FIG. 1. The program code 112 includes a Non AccessStratum (NAS) 200, a Layer 3 202, and a Layer 2 206, and is coupled to aLayer 1 218. The NAS 200 can generate NAS messages for realizing NASapplications. The Layer 3 202 is composed of an RRC layer, forperforming radio resource control. The Layer 2 206 performs linkcontrol, and the Layer 1 218 performs physical connections. Whether aPDCP layer belongs to the Layer 3 202 or the Layer 2 206 is not relevantto this invention.

In order to achieve timing alignment and resource request, a RACH isconfigured in the communications device 100 for the random accessprocedure. In such a situation, the embodiment of the present inventionprovides a RA processing program code 220 for handling a random accessprocedure, so as to prevent the prior art problems. In the following,definitions of the messages 1, 2, 3, 4 are the same as what mentionedabove. That is, the message 1 is corresponding to step “Random AccessPreamble on RACH in uplink”, the message 2 is corresponding to step“Random Access Response on DL-SCH”, the message 3 is corresponding tostep “First scheduled UL transmission on UL-SCH”, and the message 4 iscorresponding to step “Contention Resolution on DL-SCH.”

Please refer to FIG. 3, which illustrates a schematic diagram of aprocess 30 according an embodiment of the present invention. The process30 is utilized for handling a random access procedure in a UE of thewireless communications system 1200, and can be compiled into the RAprocessing program code 220. The process 30 comprises the followingsteps:

Step 300: Start.

Step 302: Decide whether to reuse the dedicated preamble when the UEdoesn't receive a downlink message successfully or the random accessprocedure is failed.

Step 304: End.

According to the process 30, the embodiment of the present decideswhether to reuse the dedicated preamble when the UE doesn't receive adownlink message successfully or the random access procedure is failed.

Preferably, deciding whether to reuse the dedicated preamble when the UEdoesn't receive a downlink message successfully or the random accessprocedure is failed is deciding whether to reuse the dedicated preamblewhen the downlink message is not successfully received after an uplinkmessage is sent. The uplink message is corresponding to a message 1corresponding to a step “Random Access Preamble on RACH in uplink” or amessage 3 corresponding to a step “First scheduled Uplink transmissionon uplink shared channel”. Deciding whether to reuse the dedicatedpreamble when the UE doesn't receive a downlink message successfully orthe random access procedure is failed comprises reusing the dedicatedpreamble or asking for another dedicated preamble, or waiting forassignment of another dedicated preamble, or releasing the dedicatedpreamble and using a random access preamble according to a standardizedrule or configuration.

Therefore, via the process 30, the embodiment of the present decideswhether to reuse the dedicated preamble when the UE doesn't receive adownlink message successfully or the random access procedure is failed.

Please refer to FIG. 4, which illustrates a schematic diagram of aprocess 40 according an embodiment of the present invention. The process40 is utilized for handling a random access procedure in a network ofthe wireless communications system 1200, and can be compiled into the RAprocessing program code 220. The process 40 comprises the followingsteps:

Step 400: Start.

Step 402: Receive a dedicated preamble for an access of a random accesschannel from a UE.

Step 404: Respond to the UE via a message 2.

Step 406: When a message 3 is not successfully received within aspecified duration or a scheduling resource, determine whether the UEreuses the dedicated preamble for next random access attempt.

Step 408: End.

According to the process 40, after the network receives a dedicatedpreamble for an access of a random access channel from a UE, the networkresponds to the UE via a message 2, and when a message 3 is notsuccessfully received within a specified duration or a schedulingresource, determine whether the UE reuses the dedicated preamble fornext random access attempt.

Preferably, the message 3 is not received when the message 3 is notdetected, or received, or is detected but not received within aspecified duration or a scheduling resource. When determining whetherthe UE reuses the dedicated preamble for next random access attempt, theembodiment of the present invention is capable of withdrawing dedicatedpreamble assigned to the UE according to a standardized rule orconfiguration, or allowing the UE to reuse the dedicated preambleaccording to a standardized rule or configuration, or assigning anotherdedicated preamble.

Therefore, via the process 40, after the network receives a dedicatedpreamble for an access of a random access channel from a UE, the networkresponds to the UE via a message 2, and when a message 3 is notsuccessfully received within a specified duration or a schedulingresource, determine whether the UE reuses the dedicated preamble fornext random access attempt.

Please refer to FIG. 5, which illustrates a schematic diagram of aprocess 50 according an embodiment of the present invention. The process50 is utilized for handling a random access procedure in a UE of thewireless communications system 1200, and can be compiled into the RAprocessing program code 220. The process 50 comprises the followingsteps:

Step 500: Start.

Step 502: Output a dedicated preamble for an access of a random accesschannel to a network.

Step 504: Receive a response from the network in a message 2.

Step 506: Determine whether to reuse the dedicated preamble according toa response from the network or whether the response is received.

Step 508: End.

According to the process 50, after the UE outputs a dedicated preamblefor an access of a random access channel to a network, the UE receives aresponse from the network in a message 2, and then the UE determineswhether to reuse the dedicated preamble according to a response from thenetwork or whether the response is received.

Preferably, when the network does not successfully receive the message 3and consider or try next random access attempt, the embodiment of thepresent is capable of asking for another dedicated preamble, or waitingfor assignment of another dedicated preamble, or releasing the dedicatedpreamble according to a standardized rule or configuration.

Therefore, via the process 50, the UE determines whether to reuse thededicated preamble according to a response from the network or whetherthe response is received.

Please refer to FIG. 6, which illustrates a schematic diagram of aprocess 60 according an embodiment of the present invention. The process60 is utilized for handling a random access procedure in a network ofthe wireless communications system 1200, and can be compiled into the RAprocessing program code 220. The process 60 comprises the followingsteps:

Step 600: Start.

Step 602: Receive a message 3 from a UE;

Step 604: Output an acknowledgement to respond the receiving status ofthe message 3.

Step 606: Determine whether a dedicated preamble of the UE can be reusedor released according to a standardized rule or configuration.

Step 608: End.

According to the process 60, after the network receives a message 3 froma UE, the network outputs an acknowledgement to respond the receivingstatus of the message 3, and determines whether a dedicated preamble ofthe UE can be reused or released according to a standardized rule orconfiguration.

Preferably, the standardized rules or configuration specifiesprocedures, rules, handlings, decision under certain condition. Theprocedures, rules, handlings, decision under certain condition comprisesdetermining whether a transmitted message 4 corresponding to acontention resolution step is a response of the message 3, whether theUE comprises another access of another random access channel for anotherrandom access procedure, whether to release or withdraw assignment ofthe dedicated preamble or allow to reuse the dedicated preamble after amessage 4 responds to the message 3, whether a message 4 correspondingto a contention resolution step is successfully transmitted orretransmitted, or whether an access of another random access channelneeds to use the dedicated preamble.

Therefore, via the process 60, after the network receives a message 3from a UE, the network outputs an acknowledgement to respond thereceiving status of the message 3, and determines whether a dedicatedpreamble of the UE can be reused or released according to a standardizedrule or configuration.

Please refer to FIG. 7, which illustrates a schematic diagram of aprocess 70 according an embodiment of the present invention. The process70 is utilized for handling a random access procedure in a UE of thewireless communications system 1200, and can be compiled into the RAprocessing program code 220. The process 70 comprises the followingsteps:

Step 700: Start.

Step 702: Use a dedicated preamble for a first random access procedure.

Step 704: Reuse the dedicated preamble for a second random accessprocedure later than the first random access procedure according to astandardized rule or configuration.

Step 706: End.

According to the process 70, after the UE uses a dedicated preamble fora first random access procedure, the embodiment of the present inventioncan reuse the dedicated preamble for a second random access procedurelater than the first random access procedure according to a standardizedrule or configuration.

Preferably, the first random access procedure is synchronization requestor handover procedure, while the second random access procedure isscheduling request, handover, synchronization request, radio linkfailure recovery, or a process indicating a network assigning thededicated preamble about the reuse of the dedicated preamble. Thestandardized rules or configuration specifies procedures, rules,handlings, decision under certain condition comprises determiningwhether the first and second random access procedures are separated fromeach other within the certain duration, or whether the grant ofresources for the first random access procedure is enough for the secondrandom access procedure, whether there is the need of a dedicatedpreamble by another access of a random access channel with higherpriority. The second random access procedure is required to use adedicated preamble. The detection/initiation of the second random accessprocedure happens during or after the said first random access procedure

Therefore, via the process 70, after the UE uses a dedicated preamblefor a first random access procedure, the embodiment of the presentinvention can reuse the dedicated preamble for a second random accessprocedure later than the first random access procedure according to astandardized rule or configuration.

Please refer to FIG. 8, which illustrates a schematic diagram of aprocess 80 according an embodiment of the present invention. The process80 is utilized for handling a random access procedure in a network ofthe wireless communications system 1200, and can be compiled into the RAprocessing program code 220. The process 80 comprises the followingsteps:

Step 800: Start.

Step 802: Assign a dedicated preamble for a UE for the random accessprocedure

Step 804: Determine whether the dedicated preamble can be reused foranother access of a random access channel or another random accessprocedure according to a standardized rule or configuration.

Step 806: End.

According to the process 80, after assigning a dedicated preamble for aUE for the random access procedure, the network determines whether thededicated preamble can be reused for another access of a random accesschannel or another random access procedure according to a standardizedrule or configuration.

Preferably, the embodiment of the present invention is capable ofindicating the UE whether to reuse the dedicated preamble when an accessof another random access channel is expected, started, or confirmed, oran access of another random access procedure occurs. The access ofanother random access channel is triggered by a synchronizationprocedure due to network initiation or a handover procedure. Indicatingthe UE whether to reuse the dedicated preamble comprises indicating theUE whether to reuse the dedicated preamble, release the dedicatedpreamble or use a new dedicated preamble or random access preamble.

Therefore, via the process 80, after assigning a dedicated preamble fora UE for the random access procedure, the network determines whether thededicated preamble can be reused for another access of a random accesschannel or another random access procedure according to a standardizedrule or configuration.

Please refer to FIG. 9, which illustrates a schematic diagram of aprocess 90 according an embodiment of the present invention. The process90 is utilized for handling a random access procedure in a network ofthe wireless communications system 1200, and can be compiled into the RAprocessing program code 220. The process 90 comprises the followingsteps:

Step 900: Start.

Step 902: Assign a dedicated preamble for a UE for an access of a randomaccess channel via a downlink message or signaling or an indication orinformation field when the random access procedure is triggered,confirmed, or expected by the network.

Step 904: End.

According to the process 90, the embodiment of the present inventionassigns a dedicated preamble for a UE for an access of a random accesschannel via a downlink message or signaling or an indication orinformation field when the random access procedure is triggered,confirmed, or expected by the network.

Preferably, the random access procedure is a synchronization due tonetwork originated call or handover access. The downlink message orsignaling is RRC, MAC, or NAS message or signaling. The initial messageor signaling is corresponding to control message or signal of a handoverprocedure, or corresponding to network originated call. The indicationor information field is a flag to indicate that there is an assignmentof a dedicated preamble, or an index to indicate which dedicatedpreamble is used in the pool, and/or a preamble field to indicate whichdedicated preamble is.

Therefore, via the process 90, the embodiment of the present inventionassigns a dedicated preamble for a UE for an access of a random accesschannel via a downlink message or signaling or an indication orinformation field when the random access procedure is triggered,confirmed, or expected by the network.

Please refer to FIG. 10, which illustrates a schematic diagram of aprocess 1000 according an embodiment of the present invention. Theprocess 1000 is utilized for handling a random access procedure in anetwork of the wireless communications system 1200, and can be compiledinto the RA processing program code 220. The process 1000 comprises thefollowing steps:

Step 1002: Start.

Step 1004: Allow the coexistence of a dedicated preamble and a randomaccess preamble corresponding to a UE according to a standardized ruleor configuration.

Step 1006: End.

According to the process 1000, the network can allow the coexistence ofa dedicated preamble and a random access preamble corresponding to a UEaccording to a standardized rule or configuration.

Therefore, via the process 1000, the network can allow the coexistenceof a dedicated preamble and a random access preamble corresponding to aUE according to a standardized rule or configuration.

Please refer to FIG. 11, which illustrates a schematic diagram of aprocess 1100 according an embodiment of the present invention. Theprocess 1100 is utilized for handling a random access procedure in a UEof the wireless communications system 1200, and can be compiled into theRA processing program code 220. The process 1100 comprises the followingsteps:

Step 1102: Start.

Step 1104: Allow the coexistence of a dedicated preamble and a randomaccess preamble for a UE for at least two random access procedures.

Step 106: End.

According to the process 1100, the UE allows the coexistence of adedicated preamble and a random access preamble for a UE for at leasttwo random access procedures.

Preferably, the UE is capable of deciding which preamble to be used forindividual procedure according to access cause, priority, QoS ofprocedures, or which procedure holds dedicated preamble for less time.Time of the dedicated preamble held by the first random access procedureis shorter

Therefore, via the process 1100, the UE allows the coexistence of adedicated preamble and a random access preamble for a UE for at leasttwo random access procedures.

In summary, the embodiment of the present invention provides differentoperations of the random access procedure, to achieve timing alignmentand resource request.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A method for handling a random access procedure in a user equipment,called UE hereinafter, of a wireless communications system, the UEassigned a dedicated preamble for the random access procedure, themethod comprising: deciding whether to reuse the dedicated preamble whenthe UE doesn't receive a downlink message successfully or the randomaccess procedure is failed.
 2. The method of claim 1, wherein thedownlink message is a message 2 corresponding to a step “Random AccessResponse on DL-SCH”, a message 4 corresponding to a step “ContentionResolution on DL-SCH”, or a response of a message 3 corresponding to astep “First scheduled Uplink transmission on uplink shared channel”. 3.The method of claim 1, wherein deciding whether to reuse the dedicatedpreamble when the UE doesn't receive a downlink message successfully orthe random access procedure is failed is deciding whether to reuse thededicated preamble when the downlink message is not successfullyreceived after an uplink message is sent.
 4. The method of claim 1,wherein the uplink message is corresponding to a message 1 correspondingto a step “Random Access Preamble on RACH in uplink” or a message 3corresponding to a step “First scheduled Uplink transmission on uplinkshared channel”.
 5. The method of claim 1, wherein deciding whether toreuse the dedicated preamble when the UE doesn't receive a downlinkmessage successfully or the random access procedure is failed comprisesreusing the dedicated preamble or asking for another dedicated preamble,or waiting for assignment of another dedicated preamble, or releasingthe dedicated preamble and using a random access preamble according to astandardized rule or configuration.
 6. A method for handling a randomaccess procedure in a network of a wireless communications systemcomprising: receiving a dedicated preamble for an access of a randomaccess channel from a user equipment, called UE hereinafter; respondingto the UE via a message 2; and when a message 3 is not successfullyreceived within a specified duration or a scheduling resource,determining whether the UE reuses the dedicated preamble for next randomaccess attempt.
 7. The method of claim 6, wherein the message 3 is notreceived when the message 3 is not detected, or received, or is detectedbut not received within a specified duration or a scheduling resource.8. The method of claim 6, wherein the message 3 is corresponding to astep “First scheduled Uplink transmission on uplink shared channel”. 9.The method of claim 6, further comprising when determining whether theUE reuses the dedicated preamble for next random access attempt,withdrawing dedicated preamble assigned to the UE according to astandardized rule or configuration, or allowing the UE to reuse thededicated preamble according to a standardized rule or configuration, orassigning another dedicated preamble.
 10. A method for handling a randomaccess procedure in a user equipment, called UE hereinafter, of awireless communications system, the UE assigned a dedicated preamble forthe random access procedure, the method comprising: outputting adedicated preamble for an access of a random access channel to anetwork; receiving a response from the network in a message 2; anddetermining whether to reuse the dedicated preamble according to aresponse from the network or whether the response is received.
 11. Themethod of claim 10, wherein the message 3 is corresponding to a step“First scheduled Uplink transmission on uplink shared channel”.
 12. Themethod of claim 10, further comprising when the network does notsuccessfully receive the message 3 and consider or try next randomaccess attempt, asking for another dedicated preamble, or waiting forassignment of another dedicated preamble, or releasing the dedicatedpreamble according to a standardized rule or configuration.
 13. A methodfor handling a random access procedure in a network of a wirelesscommunications system comprising: receiving a message 3 from a userequipment, called UE hereinafter; outputting an acknowledgement torespond the receiving status of the message 3; and determining whether adedicated preamble of the UE can be reused or released according to astandardized rule or configuration.
 14. The method of claim 13, whereinthe message 3 is corresponding to a step “First scheduled Uplinktransmission on uplink shared channel”.
 15. The method of claim 13,wherein the standardized rules or configuration specifies procedures,rules, handlings, decision under certain condition.
 16. The method ofclaim 15, wherein the procedures, rules, handlings, decision undercertain condition comprises determining whether a transmitted message 4corresponding to a contention resolution step is a response of themessage 3, whether the UE comprises another access of another randomaccess channel for another random access procedure, whether to releaseor withdraw assignment of the dedicated preamble or allow to reuse thededicated preamble after a message 4 responds to the message 3, whethera message 4 corresponding to a contention resolution step issuccessfully transmitted or retransmitted, or whether an access ofanother random access channel needs to use the dedicated preamble.
 17. Amethod for handling a random access procedure in a user equipment,called UE hereinafter, of a wireless communications system comprising:using a dedicated preamble for a first random access procedure; andreusing the dedicated preamble for a second random access procedurelater than the first random access procedure according to a standardizedrule or configuration.
 18. The method of claim 17, wherein the firstrandom access procedure is synchronization request or handoverprocedure.
 19. The method of claim 17, wherein the second random accessprocedure is scheduling request, handover, synchronization request,radio link failure recovery, or a process indicating a network assigningthe dedicated preamble about the reuse of the dedicated preamble. 20.The method of claim 17, wherein the standardized rules or configurationspecifies procedures, rules, handlings, decision under certain conditioncomprises determining whether the first and second random accessprocedures are separated from each other within the certain duration, orwhether the grant of resources for the first random access procedure isenough for the second random access procedure, whether there is the needof a dedicated preamble by another access of a random access channelwith higher priority.
 21. The method of claim 17, wherein the secondrandom access procedure is required to use a dedicated preamble.
 22. Themethod of claim 17, wherein the detection or initiation of the secondrandom access procedure happens during or after the said first randomaccess procedure.
 23. A method for handling a random access procedure ina network of a wireless communications system comprising: assigning adedicated preamble for a user equipment, called UE hereinafter, for therandom access procedure; and determining whether the dedicated preamblecan be reused for another access of a random access channel or anotherrandom access procedure according to a standardized rule orconfiguration.
 24. The method of claim 23, further comprising indicatingthe UE whether to reuse the dedicated preamble when an access of anotherrandom access channel is expected, started, or confirmed, or an accessof another random access procedure occurs.
 25. The method of claim 24,wherein the access of another random access channel is triggered by asynchronization procedure due to network initiation or a handoverprocedure.
 26. The method of claim 24, wherein indicating the UE whetherto reuse the dedicated preamble comprises indicating the UE whether toreuse the dedicated preamble, release the dedicated preamble or use anew dedicated preamble or random access preamble.
 27. A method forhandling a random access procedure in a user equipment, called UEhereinafter, of a wireless communications system, the UE assigned adedicated preamble for the random access procedure, the methodcomprising: using the dedicated preamble in an access of a random accesschannel according to configuration indicated by a control message froman upper layer.
 28. The method of claim 27, wherein the upper layerindicates at least a lower layer to use the dedicated preamble accordingto configuration indicated by the control message.
 29. The method ofclaim 27, wherein the configuration indicated by the control message isconveyed in an assignment signal or signaling of the dedicated preamble.30. A method for handling a random access procedure in a network of awireless communications system comprising: assigning a dedicatedpreamble for a user equipment, called UE hereinafter, for an access of arandom access channel via a downlink message or signaling or anindication or information field when the random access procedure istriggered, confirmed, or expected by the network.
 31. The method ofclaim 30, wherein the random access procedure is a synchronization dueto network originated call or handover access.
 32. The method of claim30, wherein the downlink message or signaling is RRC, MAC, or NASmessage or signaling.
 33. The method of claim 30, wherein the initialmessage or signaling is corresponding to control message or signal of ahandover procedure, or corresponding to network originated call.
 34. Themethod of claim 30, wherein the indication or information field is aflag to indicate that there is an assignment of a dedicated preamble, oran index to indicate which dedicated preamble is used in the pool,and/or a preamble field to indicate which dedicated preamble is.
 35. Amethod for handling a random access procedure in a network of a wirelesscommunications system comprising: allowing the coexistence of adedicated preamble and a random access preamble corresponding to a userequipment, called UE hereinafter, according to a standardized rule orconfiguration.
 36. A method for handling a random access procedure in auser equipment, called UE hereinafter, of a wireless communicationssystem comprising: allowing the coexistence of a dedicated preamble anda random access preamble for a UE for at least two random accessprocedures.
 37. The method of claim 36 further comprising deciding whichpreamble to be used for individual procedure according to access cause,priority, QoS of procedures, or which procedure holds dedicated preamblefor less time.
 38. The method of claim 37, wherein time of the dedicatedpreamble held by the first random access procedure is shorter.
 39. Acommunications device for accurately handling a random access procedurein a wireless communications system comprising: a control circuit forrealizing functions of the communications device; a processor installedin the control circuit, for executing a program code to command thecontrol circuit; and a memory installed in the control circuit andcoupled to the processor for storing the program code; wherein theprogram code comprises: the communications device assigned a dedicatedpreamble for the random access procedure; and deciding whether to reusethe dedicated preamble when the UE doesn't receive a downlink messagesuccessfully or the random access procedure is failed.
 40. Acommunications device for accurately handling a random access procedurein a wireless communications system comprising: a control circuit forrealizing functions of the communications device; a processor installedin the control circuit, for executing a program code to command thecontrol circuit; and a memory installed in the control circuit andcoupled to the processor for storing the program code; wherein theprogram code comprises: receiving a dedicated preamble for an access ofa random access channel from a user equipment, called UE hereinafter;responding to the UE via a message 2; and when a message 3 is notsuccessfully received within a specified duration or a schedulingresource, determining whether the UE reuses the dedicated preamble fornext random access attempt.
 41. A communications device for accuratelyhandling a random access procedure in a wireless communications systemcomprising: a control circuit for realizing functions of thecommunications device; a processor installed in the control circuit, forexecuting a program code to command the control circuit; and a memoryinstalled in the control circuit and coupled to the processor forstoring the program code; wherein the program code comprises: thecommunications device assigned a dedicated preamble for the randomaccess procedure; outputting a dedicated preamble for an access of arandom access channel to a network; receiving a response from thenetwork in a message 2; and determining whether to reuse the dedicatedpreamble according to a response from the network or whether theresponse is received.
 42. A communications device for accuratelyhandling a random access procedure in a wireless communications systemcomprising: a control circuit for realizing functions of thecommunications device; a processor installed in the control circuit, forexecuting a program code to command the control circuit; and a memoryinstalled in the control circuit and coupled to the processor forstoring the program code; wherein the program code comprises: receivinga message 3 from a user equipment, called UE hereinafter; outputting anacknowledgement to respond the receiving status of the message 3; anddetermining whether a dedicated preamble of the UE can be reused orreleased according to a standardized rule or configuration.
 43. Acommunications device for accurately handling a random access procedurein a wireless communications system comprising: a control circuit forrealizing functions of the communications device; a processor installedin the control circuit, for executing a program code to command thecontrol circuit; and a memory installed in the control circuit andcoupled to the processor for storing the program code; wherein theprogram code comprises: using a dedicated preamble for a first randomaccess procedure; and reusing the dedicated preamble for a second randomaccess procedure later than the first random access procedure accordingto a standardized rule or configuration.
 44. A communications device foraccurately handling a random access procedure in a wirelesscommunications system comprising: a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises: assigning a dedicated preamble for a user equipment, calledUE hereinafter, for the random access procedure; and determining whetherthe dedicated preamble can be reused for another access of a randomaccess channel or another random access procedure according to astandardized rule or configuration.
 45. A communications device foraccurately handling a random access procedure in a wirelesscommunications system comprising: a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises: the communications device assigned a dedicated preamble forthe random access procedure; and using the dedicated preamble in anaccess of a random access channel according to configuration indicatedby a control message from an upper layer.
 46. A communications devicefor accurately handling a random access procedure in a wirelesscommunications system comprising: a control circuit for realizingfunctions of the communications device; a processor installed in thecontrol circuit, for executing a program code to command the controlcircuit; and a memory installed in the control circuit and coupled tothe processor for storing the program code; wherein the program codecomprises: assigning a dedicated preamble for a user equipment, calledUE hereinafter, for an access of a random access channel via a downlinkmessage or signaling or an indication or information field when therandom access procedure is triggered, confirmed, or expected by thenetwork.
 47. A communications device for accurately handling a randomaccess procedure in a wireless communications system comprising: acontrol circuit for realizing functions of the communications device; aprocessor installed in the control circuit, for executing a program codeto command the control circuit; and a memory installed in the controlcircuit and coupled to the processor for storing the program code;wherein the program code comprises: allowing the coexistence of adedicated preamble and a random access preamble corresponding to a userequipment, called UE hereinafter, according to a standardized rule orconfiguration.
 48. A communications device for accurately handling arandom access procedure in a wireless communications system comprising:a control circuit for realizing functions of the communications device;a processor installed in the control circuit, for executing a programcode to command the control circuit; and a memory installed in thecontrol circuit and coupled to the processor for storing the programcode; wherein the program code comprises: allowing the coexistence of adedicated preamble and a random access preamble for a UE for at leasttwo random access procedures.